Question

Seismographs rely heavily on a pendulum (free-swinging weight) to record measurements. How do you think using a pendulum helps detect small earthquakes?

Answer 1

Principle of a pendulum: a heavy, inert mass with a certain resistance to movement (i.e. inertia) due to its weight is suspended from a frame by a spring that allows movement. The energy from any seismic activity excites this “proof mass” as it is called by geophysicists, making it vibrate. When they detect movement, such as the shifting plates of an earthquake, a pendulum with a pen attached to it graphs the magnitude of the movement. If the pendulum swings vigorously, scientists know that the seismic waves are intense and potentially dangerous. My guess is, when pendulum swings lightly it determines mild intensity and small impact of an earthquake.

Answer 2

Generally, a seismograph consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper, magnetic tape, or another recording medium.